The present invention relates generally to the field of power electronic devices such as those used in power conversion or to apply power to motors and similar loads. More particularly, the invention relates to an improved inductor arrangement which can be incorporated in a modular fashion in various circuits and which provides enhanced component integration and thermal characteristics.
In the field of power electronic devices, a wide range of circuitry is known and currently available for converting, producing and applying power to loads. Depending upon the application, such circuitry may convert incoming power from one form to another as needed by the load. In a typical arrangement, for example, constant (or varying) frequency alternating current power (such as from a utility grid or generator) is converted to controlled frequency alternating current power to drive motors, and other loads. In this type of application, the frequency of the output power can be regulated to control the speed of the motor or other device. Many other applications exist, however, for power electronic circuits which can convert alternating current power to direct current power, or vice versa, or that otherwise manipulate, filter, or modify electric signals for powering a load. Circuits of this type generally include inverters, converters, and similar switched circuitry. Other applications include universal power controllers, micro-turbine generators, universal power sources, and so forth.
Many power electronic circuits of the type mentioned above require filtration through the use of chokes or inductors used on either a line side or a load side of the circuitry, or both. Such inductors serve to limit current, shape waveforms and improve harmonics. In addition, certain circuitry may employ direct current link inductors, such as between two inverter circuits in a drive application. Common mode inductors are also employed, depending upon the system requirements.
Depending upon the system configuration, input and output power levels, frequencies, and so forth, chokes and inductors used in power electronic circuits can be quite sizeable. The physical packaging in such applications becomes problematic, both from mounting and interconnection standpoints. Furthermore, due to the inherent functionality of the inductors, large amounts of heat may be generated during operation which must be dissipated to maintain the internal temperatures of the inductor within a desired thermal operating range. In large packaged inductors, such thermal management becomes extremely problematic. For example, currently available inductors that can be scaled to power electronic circuits include packaging configurations in which a bundle of conductive wire is disposed within an encapsulated shell. A potting material, typically epoxy, is disposed within the shell to seal the structure. These structures are not, however, completely modular in design, and require termination of leads extending from the shell. While a certain amount of cooling can be provided against a face of the shell, and cooling conductors can be routed through an aperture formed in the shell, these measures are typically insufficient to develop the desired level of cooling of interior regions of the structure. Moreover, the axial winding (conductors wrapped about the central axis perpendicular to the mounting base) makes further extensions of cooling surfaces difficult or impossible.
In addition to the packaging and cooling considerations mentioned above, modularity could be a useful feature of inductor structures. However, as mentioned, very little if any modularity is provided in existing inductor packaging. Furthermore, current inductors incorporate little or no additional circuitry. Such additional circuitry, that would be useful in packaged modular inductors may include integrated current sensors, ground fault sensing arrangements, capacitors, voltage sensors, integrated common mode inductor and link inductor packages, and so forth. Such arrangements are currently unavailable with existing technologies.
There is a need, therefore, for improved choke or inductor arrangements. There is a particular need for inductors which can be configured and packaged to provide modularity, enhanced thermal characteristics, and possible integration of additional components and circuitry into the same modular package.